Recently, high performance is progressed in mobile communication devices represented by smart phones or mobile phones. For example, handling is rapidly shifted from a third generation system to an LTE (Long Term Evolution). In the LTE, a data communication of a large capacity is performed with a higher speed. Therefore, specs demanded for high frequency components becomes higher. Reduction of an insertion loss of filters or duplexers using an acoustic wave device is being demanded. There are acoustic wave devices in which an IDT (Interdigital Transducer) is provided on a piezoelectric substrate such as surface acoustic wave devices, as acoustic wave devices used in mobile communication devices or the like.
Japanese Patent Application Publications No. 2000-341073, No. 2003-87083, No. 2008-113273, No. 11-298286 and No. 2013-518455 disclose that gratings are provided on both sides of an IDT in an aperture direction thereof in a surface acoustic wave device.